This invention relates to producing castings of silicone elastomers from solvent-based silicone dispersions using a hollow mold and multi-axis rotation until the material devolatilizes to a non-flowable state and is cured.
Rotational molding of many industrial, consumer, and medical related parts from a variety of plastics is commonplace. The plastic materials are typically polyolefins in pellet or powder form, but some are flowable liquids, such as plastisols, with sufficiently low viscosity, i.e. less than 5000 cps.
The rotational molding or casting method and system of the present invention has utility in the manufacture of breast implants and other medical devices and articles having a thin-walled shell, typically formed from silicone elastomer, such as tissue expanders and low-pressure elastomeric balloons. Low-pressure elastomeric balloons are used, for example, in catheter fixation, occlusion of blood flow, bracytherapy, and as intraaortic or intragastric balloons for cardiovascular or ear-nose-and-throat procedures. Other articles include feeding tubes, enema cuffs, catheters, condoms, shunts, and embolic protection devices. The traditional method of manufacturing these articles is by dipping a mandrel in a solvent-based silicone dispersion to cast and form the shell.
A system and method for molding the shell of a medical device or other molded article is disclosed. The system includes a multi-axis rotational molding machine in which a mold is mounted. The mold has a cavity in the shape of the article to be molded. The mold seals to hold a vacuum.
In operation, silicone or other molding material is inserted into the mold, vacuum is applied to the mold, the mold is rotated about at least two axes and a molding material coats the inside walls of the mold to form the shell or other desired article.
A rotationally molded medical article is also disclosed.